There has been great interest in the analysis of small RNAs, such as short interfering RNAs (siRNAs), microRNAs (miRNA), tiny non-codingRNAs (mcRNA) and small modulatory RNA (smRNA), since the discovery of sRNA biological activity over a decade ago. See Novina et al., Nature 430: 161-164 (2004). Even though the functions of most discovered miRNAs remain a mystery, it has become clear that they exist in abundance in plants and animals, with up to tens of thousands of copies per cell. In the fruit fly, 78 have been identified, and over 200 have been identified in human (see the public database accessible via the website located at sanger.ac.uk/cqi-bin/Rfam/mirna/browse.pl). The levels of individual miRNAs seem to vary with developmental stages and tissue types. The level of fluctuation may be correlated with phenotype, mRNA levels, or protein levels for better biological insight. Thus quantitative measurements of miRNA may be of great importance. Further, viral miRNAs have been identified and may play a role in latency (see Pfeffer et al., Science, 304: 734-736 (2004)), making the detection and quantification of miRNAs a potentially valuable diagnostic tool.
Straightforward and reliable methods for simultaneously analyzing several constituents of a complex RNA sample are extremely desirable. While current methods of preparing RNA samples are quite useful, there is a continuing need for methods of preparing RNA samples for analysis or for other purposes.